Self-locking automatically-releasing sash balance for removable sash windows



Aug. 3, 1965 TROUT 3,197,819

D. SELF-LOCKING AUTOMATICALLY-RELEASING SASH BALANCE FOR REMOVABLE SASH WINDOWS Filed March 25, 1963 2 Sheets-Sheet 1 JNVENTOR.

DON/M0 M TROUT kwv Aug. 3, 1965 M. TRO

D. UT SELF-LOCKING AUTOMATICALLY-RELEASING SASH BALANCE FOR REMOVABLE SASH WINDOWS Filed March 25, 1963 2 Sheets-Sheet 2 6 IN VEN TOR.

DONAL D M. 7 90 U 7' United States Patent ELF LGEKING AUTEMATECALLY RELEASTNG EALANEE FUR REMOVABLE SASH WENDUWS Donald M. Trout, 15373 Greenfield, Apt. 4, Detroit 27, Mich. Filed Mar. 25, 1%3, Ser. No, 267,678 8 Claims. (El. 20-523) This invention relates to sash balances for removable sash windows and, in particular, to self-locking sash balances for such windows.

One object of this invention is to provide a self-locking automatically-releasing sash balance for removable sash windows wherein the locking device is of simpler, less expensive and more rugged construction and of more positive and non-slipping action than the locking devices of prior self-locking sash balances in that it contains only two working parts and is operated by a counterweight on the locking member without requiring the aid either of an auxiliary spring or of the sash balancing spring itself.

Another object is to provide a self-locking automatically-releasing sash balance of the foregoing character which is of more compact construction than prior selflocking sash balances in that it employs a thinner guide block while obtaining an adequate length of lever arm, so that it fits into the more limited space available in the newer channel sash guides, such as that required to fit the so-called modular frame recommended for standardization by the US. Department of Commerce.

Another object is to provide a self-locking automatically-releasing sash balance of the foregoing character wherein none of the parts thereof requires any machining and wherein the assembly is accomplished simply by pushing or dropping the locldng member into the guide block.

Another object is to provide a self-locking automatically-releasing sash balance of the foregoing character wherein the locking member does not require extremely sharp edges or corners for its locking action, as heretofore required, and can even employ rounded corners or edges, hence causes less indentation and consequently less mutilation of the sash guide channel, which it engages on the invisible inner side thereof.

Another object is to provide a self-locking automatically-releasing sash balance of the foregoing character wherein the guide block merely exerts a guiding action and carries and retains the locking member without itself exerting any locking action; and wherein the point of attachment of the balancing spring or balancing weight cable to the guide block is not critical but can be located at any suitable place on the guide block.

Another object is to provide a self-locking automatically-releasing sash balance of the foregoing character wherein the locking member rocks upon a fulcrum provided by a guide block without the need for the extra machining required by the use of a fulcrum pin which, however, may, if desired, be employed in a modified form of the invention. r

Another object is to provide a modified form of the invention wherein the balancing spring, instead of comprising a tension spring located above the guide block as in the principal form of the invention, comprises a compression spring located below the guide block.

Other objects and advantages of the invention will become apparent during the course of the following description of the accompanying drawings, wherein FIGURE 1 is a fragmentary front elevation of a removable sash window installation equipped with the selflocking automatically-releasing sash balance of the present invention, partly in vertical section along the line 11 Eatented 3, 1955 in FIGURE 2, with the sash balance in its unlocked position;

FIGURE 2 is a horizontal section through the removable sash window installation of FIGURE 1, taken along the line 2-2 in FIGURE 1 and also showing the opposite side of the window frame and sash guide from that shown in FIGURE 1;

FIGURE 3 is an enlarged view of the sash balance locking and releasing unit shown in the right-hand central portion of FIGURE 1, but on a larger scale;

FIGURE 4 is a view similar to FIGURE 3, but with the sash removed and the sash balance consequently in its locked position;

FEGURE 5 is a vertical cross-section, mainly in front elevation, of the sash balance locking unit shown in FIG- URE 4;

FIGURE 6 is a horizontal section, mainly in top plan view, taken along the line 66 in FIGURE 4;

FIGURE 7 is a crosssection through the releasing device for the sash balance of the present invention, taken along the line 7--'7 in FIGURE 3;

FIGURE 8 is a fragmentary vertical section similar to FIGURE 4, but showing a slight modification of the present invention in its unlocked position, with the releasing plunger shown in dotted lines; and

FEGURE 9 is a View similar to FIGURES 4 and 8, but of a further modification, wherein a pivot pin is employed in place of a fulcrum edge.

Referring to the drawings in detail, FEGURES 1 and 2 show a removable sash window installation, generally designated it according to one form of the invention as consisting generally of a window frame 12 containing on one side a fixed channel sash guide 14 and on the opposite side a resiliently-mounted channel sash guide 16 containing hollow integral sash guide ribs 18 and 26 respectively. The hollow guide ribs 18 serve as casings for self-locking automatically-releasing sash balances, generally designated 22, of which one only is shown in FIGURE 2, the other one, for the upper sash, being above the section plane and hence not shown in FIGURE 2. The sash balances 22 engage and counterbalance the weights of upper and lower double-hung sliding sashes 24 and 26 respectively (FIGURE 1). The upper and lower sashes 24 and 26 are of substantially identical construction, hence a description of the lower sash 26 and its accompanying sash balance 22 will serve as a description for that of the upper sash 24 without the necessity of duplicating such description.

The window installation ltl possesses a conventional window frame 12 which has the usual side members 28 interconnected by a top member 36 and a bottom member or sill 32 (FIGURE 1) and the upper and lower sashes Z4 and 26 are equipped with the usual window panes 34 and 35 respectively. The upper sash 24 is provided with a top rail 38 and opposite side rails 49, the bottom or meeting rail thereof being omitted as unnecessary for the disclosure of the present invention. The lower sash 2a is provided with the usual bottom rail 42 and opposite side rails 44, the top rail or meeting rail thereof being likewise omitted as unnecessary for the disclosure of the present invention.

lower sashes 2d and as also contain recesses or bores 52 extending inwardly from the guide grooves 46 and con- 35 taining sash balance releasing devices, generally designated 54 (FIGURES 1, 2, 3 and 7).

Each sash balance releasing device 54 consists of an approximately tubular casing 56 having prongs 555 projecting outwardly therefrom for interpenetrating engagement with the sash rails iber 44 when the casing 56 is driven into its respective hole 54 by means of a hammer or other pushing device. The prongs 58 are inclined as at 60 on their entering side and shouldered as at 62 (FIGURE 3) on the opposite side so as to resist removal or rotation of the casing 56. The latter is of cylindrical or cup-shaped form with a longitudinal bore 64 therein of substantially rectangular cross-section (FIGURE 7) and a longitudinal slot 66 in the bottom thereof loosely and slidably receiving a lug 63 projecting downwardly from the bottom of a lock-releasing elongated plunger '71) likewise of rectangular cross-section Slidably engaging the bore 64. The plunger 70 is urged outwardly from its casing bore 64 by a helical compression spring '72, the rearward end of which engages the rear wall '74 of the casing 56 and the forward end of which engages the rearward end 76 of the lock-releasing plunger 7%.

The forward end 78 of the plunger 70 has a rounded The spring chambers 99 are of rectangular cross-section (FIGURE 2).

The fixed channel sash guide 14 and the resilientlymounted sash guide 16 are of similar construction and each is preferably extruded from a suitable metal, such as aluminum. The front wall 5ft at its opposite edge is provided with rearwardly-extending flanges 92 which slidably engage the adjacent surfaces of the window frame members 94 and 96 respectively located on opposite sides of the window frame side members 28 (FIGURE 2). The front walls 5t) of the channel guide members 14 and 15 are provided at vertically-spaced intervals with conical indentations 98 (FIGURE 2) terminating in holes 1% which respectively receive the heads and shanks of fasteners 16?. and 104 threaded into the adjacent window frame side members 28. The fasteners 102 and 1M- are preferably wood screws of similar construction but of different lengths, the fastener 1% being of greater length in order to accommodate helical compression springs 11% which resiliently support the channel guide member i The springs 11% at their rearward ends are seated in cup-shaped socket 1% drilled in the side member 28 at vertically-spaced intervals along the adjacent side member 28 and their forward ends yieldingly engage the rearward walls 11% of the hollow guide rib portions 21 Slidably mounted within each chamber 9% of each hollow guide rib 13 of the channel sash guide 14 is the sash balancing tension spring 112 of a self-locking automatically-releasing sash balance, generally designated 114, containing at its lower end a locking unit 116. The upper end loop 113 of the balancing spring 112 is secured to the upper end 1% of the guide rib 18 in any suitable manner, such as by hooking it over the upper end 120.

The lower end loop 122 of the balancing spring 112 (FIGURES 3, 4 and 5) is hooked through a hole 124 in a lug 126 projecting upward from the upper rearward cross member 128 of a guide block or lock carrier 1313. The guide block or lock carrier tea is formed from any suitable material such as the polyamide plastic known commercially as nylon, and is of rectangular cross-section (FIGURE 6) adapted to loosely and slidably fit the rectangular cross-section of the chamber 9h. At its lower end the guide block 13% has a lower forward cross member 132 (FIGURE 4), the top portion 134 of which has a flattened upper surface 135 provided with a rearward, preferably sharp, fulcrum edge 136. The upper portion 134 of the cross member 132 has an inclined flat forward surface 138 leading downward to the forward surface 144} of the guide block 1311 from the upper surface 135.

Rearward of the lower forward cross member 132 and below the upper rearward cross member 123, the guide block 131) is provided with an approximately Z- shaped slot or cavity 142 which extends from the front surface 149 to the rear surface 144 between opposite parallel side walls 156 (FIGURES 5 and 6) of the guide block 13%. The flat vertical lateral surfaces 152 of the side walls 15! loosely and Slidably engage the side walls 154 of the hollow guide ribs 18 while the forward surface Iidd loosely and slidably engages the front wall flanges 88. The rearsurface 144 of the guide block 13d is centrally grooved longitudinally as at 158 to provide spaced parallel lands 16% (FIGURE 6) which slidably engage the rear wall of each hollow guide rib 13.

Tiltably mounted on the fulcrum edge 136 and adjacent upper surface of the forward cross member 132 on the guide block or lock carrier 131) is an approximately T-shaped locking member, generally designated 162, of sintered powdered iron, steel or other suitable material. The locking member 162 has an approximately horizontal forward trigger arm 166 disposed forward of the fulcrum edge 136 and a rearward overweight locking arm disposed rearwardly of the fulcrum edge 1% and including a lower overweight or overbalancing weight arm portion 16% and an upper locking arm portion 168 projecting respectively downwardly from and upwardly from the trigger arm 166. The trigger arm 166 near its junction with the overweight locking arm 165 is provided with a transversely-extending horizontal groove 179 of truncated V-shaped cross-section having a slightly greater angular extent than the upper surface 135 adjacent the fulcrum edge 136 on the lower forward cross member 132 of the lock carrier 1% and having a preferably sharp rearward contact portion 172 constituting a fulcrum rest engageable with the fulcrum edge 136. The central portion 174 of the groove 17% is substantially flat to approximately match the upper surface 135 of the upper portion 134 of the cross member 132. The greater angle between the front and rear surfaces 176 and 178 of the groove 1'70 provides clearance for tilting or rocking of the locking member 162 upon the fulcrum edge 136, as shown by the contrasting positions thereof in FIGURES 3 and 4.

The lower arm portion 164 of the overweight locking arm 165 extends downwardly a sufficient distance to provide suflicient overweight action to cause the locking member 162 to rock normally into the inclined position shown in FIGURE 4 in the absence of the sash and its plunger 70 to urge it in the upright position of FIGURE 3. The upper locking arm portion 168 above the lower arm portion 164 is provided with a rearward locking edge 18% (FIGURE 4) which is preferably sharp for slightly indenting the rearward wall 110 of the hollow guide ribs 18 to provide accentuated locking action. Locking action, however, may also be efiected with less indentation and consequently less marring of the inner surface of the rearward wall 110 if the locking edge 18!) is dull, as by being slightly rounded. The horizontal arm 166 of the locking member 162 is provided with an upper surface 182 which is engageable with the lower surface 82 0f the plunger 719 when the sash is in its inserted position within the window frame 12 (FIGURES 1, 2 and 3).

The modified self-locking automatically-releasing sash balance, generally designated 1%, shown in FIGURE 8 notch has a balancing spring 112 similar to that of the sash balance 114 and differs in the construction of its locking device, here generally designated 192. The latter has a guide block or lock carrier 194 withfan upstanding bridge member 1% joining the upper ends of parallel side walls 198 and having a hole 201 through which the lower end loop 122 of the balancing spring 112 is hooked. The parallel vertical side walls 198 are joined at the front and rear surfaces 2% and 202 respectively by forward and rearward cross members 264 and 206 respectively. The guide block or lock carrier 124 by reason of this construction possesses a passageway 20% between the opposite side walls 198 in which is mounted a locking member 211) having an obtuse-angled notch'212 separating horizontal and vertical arms 214 and 216 respectively and having a junction line or fulcrum rest 218 adapted to pivot upon the upper rearward fulcrum edge 221) which forms the junction of the horizontal top surface 222 and vertical rear surface 224 of the cross member 2114. The notch 212 has upper and lower surfaces 226 and 228 which, as stated above, are inclined at obtuse angles to one another so as to provide clearance for. tilting or rocking of the locking member 21%) upon the fulcrum edge 220, which is preferably sharp.

The locking member 2111, as before, has an upstanding extension 23% of the vertical arm 216 terminating at its upper rearward end in a locking edge 232 which is preferably sharp. The horizontal ar1n214 has an upper surface 234 which is engageable with the lower surface 82 of the unlocking plunger 76, shown in dotted lines in FIGURE 8, cross member 2116 acting as a stop.

The further modified self-locking automatically-releasing sash balance, generally designated 240, shown in FIG- URE 9 is generally similar in construction to the selflocking sash balance 1% of FIGURE 8 and corresponding parts are designated withthe same reference numerals. In the modified sash balance 249, the guide block or lock carrier 242 lacks the lower'rearward. cross member 2% or" FIGURE 8, because its stop action is unnecessary in view of the fact that the side walls 198 are drilled horizontally in alignment adjacent the fulcrum edge 21% of the cross member 204 to receive the opposite ends of a pivot pin 244 which constitutes a fulcrum and which also passes through a hole 245 in the locking member 246, the hole 245 constituting a fulcrum rest. The'latter is of generally similar shape to the locking member 210 of FIGURE 8, and, like it, has a rearward upper locking edge 248 which is preferably sharp for indenting the rear wall 111) of the hollow guide rib 18 but may also be somewhat dull to lessen the indentations made in the rear wall 110. The upper bridge member which interconnects the opposite side walls 195 as before has a hole 20:) therein through which the lower end loop 122 of the balancing spring 112 is hooked, as in the sash baiance 1% of FIGURE 8. The locking member 246 has horizontal and vertical arms 258 and 252 respectively with surfaces 254 and 256 of an obtuse-angled The horizontal arm 2511 has an upper surface 269 which is engaged by the lower surface 82 of the releasing plunger 71}, as shown in dotted lines in FIGURE 9. K I

In the assembly of the self-lockingsash balance 114 l of FIGURES 1 to 7 inclusive and of the self-locking sash balance 1% of FIGURE 8, the locking devices 116 and 122 are quickly and easily assembled by dropping or pushing the hammer-shaped locking members 162 or 210 into the passageways 142 or 298 of their respective guide blocks or lock carriers 130 or 194 so that their notches 174 or 212 rest upon thefulcrum edges 136 or 221 of their respective lower cross members 132 or 264 (FIGURES 4 and 8 respectively). 242 of FIGURE 9 is similarly assembled, except that the pivot pin 214 is pushed through the drilled side walls 1% and through the hole 245 in thelocking member 246 during such assembly. The lower loop 122 of the bal- The locking device ancing spring 112 is hooked through its respective-hole 124 or 201 of the upper cross memberor bridge member 126 or 1% respectively and the upper loop 118 hooked over the upper end 12 3 of the guide rib 151.

In the operation of the sash balance 114 of FIGURES 1 to 7 inclusive, let it be assumed that the sash 26 is in its normal position within the window frame 12 and that j the lower surface 82 of the plunger 70 is engaging the upper surface 132 of the horizontal arm 166 of .the locking member 162, thereby tilting the latter around the fulcrum edge 136 of the guide block or lock carrier 13% and consequently disengaging the locking edge 1811 thereof from the rearward wail 11E) of the hollow guide rib 18 of the guide channel 14 (FIGURES 1 and 3). As a result the guide block or lock carrier 130 is free to move upward or downward within the chamber 90 as the sash 26 is raised or lowered, in accordance with the pull exerted by the balancing spring 112. A similar action occurs with the corresponding sash balance 114 (not shown) for the upper sash 24.

To remove the lower sash 26, the operator pushes sidewise thereon (to the left in FIGURES 1 and 2), thereby causing the left-hand side rail 44 to push the left-hand resiliently-mounted channel sash guide 16 to the left, compressing itsf'mounting springs 1% until the guide groove 46 in the right-hand" vertical sash rail 44 clears the forwardly-projecting guide portion 48 of its respec tive hollow guide rib 18. The operator then swings the sash 26 around a vertical axis pivoting on the left-hand guide rib 20 while he swings the right-hand sash rail 44 toward himself, thereby sliding the releasing plunger 76 off the upper surface 182 of the horizontal arm 166 of the locking member 162. The preponderant weight of the lower or vertical arm 164 thereof acting around the fulcrum edge 136 swings the locking member 162 clockwise into the tilted position shown in FIGURE 4 as the balancing spring 112 pullsupward upon the guide block or lock carrier 130. This action causes the locking edge 131) of the locking member 162 to dig into the rear wall 110, locking the locking member 162 and the locking device 116 in their attained positions.

The sash 26 may be replaced in the window frame by reversing the foregoing procedure. If the plunger '71 happens to be replaced above the locking device 116, a downward pull on the sash 26: engages its lower surface .82 with the upper surface 182 of the locking member 162,

tilting the latter about the fulcrum edge 136 from the position of FIGURE 4 tothe position of FIGURE 3. This action disengages the locking edge 131 from the rear wall 110 and releases the guide block or look carrier 13% to move upward or downward in response to the pull of the balancing spring 112.

The operation of the modified self-locking sash balances 1% of FIGURE 8 and 2 36 of FIGURE 9 is similar and hence requires no repetition of the above description thereof. In the locking device 192 of FIGURE 8, as previously stated above, the cross member 296 serves as a rearward stop for the tilting locking member 210, whereas the pivot pin 244 on the locking member 246 of FIGURE 9 retains the locking member 246 in position without the need for the cross member a similar but oppositely-facing sash balance 22 may be installed in the hollow guide ribs 20 of the resilientlymounted sash guide 16 on the left-hand side of FIGURE 2 in the same manner as installed in therigidly-mounted sash guide 14 on the right-hand side of FIGURE 2, thereby duplicating the showing on'the right-hand side of FIGURE 2. The use of two sash balances 22 on opposite sides of each sash, namely two for the lower sash 26 and two for the upper sash 24 is preferable in installations in volving large windows. 7

It will be understood that there are two stopping actions imposed upon the tilting or rocking locking member in each form of the invention, so as to limit the rocking and also the horizontal sliding of the locking member. In the form of the invention shown in FIGURES 1 to 7 inclusive, the rocking of the locking member 162 is limited in a forward or counterclockwise direction of rotation or tilt by the engagement of the surfaces 176 and 138 of the locking member 162 and forward lower cross member 132 respectively, as well as with the engagement of the upper surface of the locking arm portion 16% adjacent the locking edge 180 of the locking member 162 with the lower surface of the upper cross member 128 of the guide block or lock carrier 130 (FIGURES 1 and 4).

In the modified self-locking automatically-releasing sash balance 1% of FIGURE 8, the stop action in a forward or counterclockwise direction is accomplished by the engagement of the lower surface 212 on the trigger arm 214 with the upper surface 222 of the lower forward cross member 2% and also by engagement of the overweight arm portion 216 with the lower rearward cross member 206.

In the further modified self-locking automatically-releasing sash balance 240 of FIGURE 9, the forward or rearward sliding of the locking member 246 is prevented by the pivot pin 244 and the forward or counterclockwise rotation thereof is limited by the engagement of the lower surface 254, of the trigger arm 250 with the upper surface 222 of the forward lower cross member 294. The prevention of forward or rearward sliding is accomplished for the purpose of preventing scraping of the sharp locking edge of the respective locking member as the sash moves up and down in the unlocked position.

What I claim is: 1. A self-locking automatically releasing sash balance for a removable sash window, comprising an elongated hollow sash balance casing having a wall structure with an elongated opening therein, a resilient sash balancing member anchored to said casing and disposed therein, a lock carrier reciprocably mounted in said casing in guided relationship therewith and having a fulcrum thereon spaced inwardly away from said opening, and an approximately T-shaped locking member disposed substantially in its entirety within said hollow casing and having a fulcrum rest tiltably engaging said fulcrum, a trigger arm extending from said fulcrum rest toward said opening and terminating subr st-antially adjacent said opening, and a preponderant locking arm having a lower arm portion of heavier weight than said trigger arm extending downwardly away from said fulcrum rest toward one of said walls and having an upper arm portion disposed above said fulcrum rest with a locking edge thereon normally urged by the preponderant weight of said lower, arm portion into locking engagement with the wall structure attalocationspaced away from said opening. 2. A self-locking automatically-releasing sash balance for a removable sash window, comprising some anelongated hollow sash balance casing having a wall 7 structure with an elongated opening therein, 7

a resilient sash balancing member anchored to said casing and disposed therein,

a lock carrier reciprocably mounted in said casing in guided relationship therewith and having .a fulcrum thereon,

and an approximately T-shaped locking member having a fulcrum rest tiltably engaging said fulcrum, a trigger arm extending from said fulcrum rest toward said opening, and a preponderant locking arm of heavier weight thansaid trigger arm extending away from said fulcrum rest toward one of said walls and having a locking edge thereonnorma'lly urged by the preponderant weight of said locking arm into locking engagement with the wall structure at a locationspaced away from said opening,

said fulcrum rest comprising the bottom of an inverted notch extending upwardly beneath said trigger arm.

3. A self-locking automatically-releasing sash balance,

according to claim 21, wherein said notch is of approximately inverted V-shaped configuration.

2-. A self-locking automatically-releasing sash balance for a removable sash window, comprising an elongated hollow sash balance casing having a wall structure with an elongated opening therein,

a resilient sash balancing member anchored to said casing and disposed therein, 7 I

alock carrier reciprocably mounted in said casing in guided relationship therewith and having a fulcrum thereon,

and an approximately T-shaped locking member having a fulcrum rest tiltably engaging said fulcrum, a trigger arm extending from said fulcrum rest toward said opening, and a preponderant locking arm of heavier weight than said trigger arm extending away from said fulcrum rest toward one of said walls and having a locking edge thereon normally urged by the preponderant weight of said locking arm into locking engagement with the wall structure at a location spaced away from said opening,

said lock carrier having a fulcrum support disposed beneath said fulcrum with a stop surface extending from said fulcrum toward said opening.

5. A. self-locking automatically-releasing sash balance,

according to claim 4, wherein said stop surface is inclined downward away from said fulcrum toward said opening.

6. A self-locking automatically-releasing sash balance,

according to claim 4, wherein said stop surface extends substantially horizontally forward from said fulcrum toward said opening. v

'7. A self-locking automatically-releasing sash balance for a removable sash window, comprising an elongated hollow sash balance casing having a wall structure with an elongated opening therein,

a resilient sash balancing member anchored to said casing and disposed therein,

a lock carrier reciprocably mounted in said casing in guided relationship therewith and having a fulcrum thereon,

and an approximately T-shaped locking member having a fulcrum rest tiltably engaging said fulcrum, a tri ger arm extending from said fulcrum rest toward said opening, and a preponderant locking arm of heavier weight than said trigger arm extending away from said fulcrum rest toward one of said walls and having a locking edge thereon normally urged by the preponderant Weight of said locking arm into locking engagement with the wall structure at a location spaced away from said opening, v

7 said fulcrum comprising a pivot member mounted upon a substantially horizontal axis disposedtransversely of said lock carrier and said locking member being pivotally mounted upon said pivot member.

8. A self-locking automatically-releasing sash balance for a removable sash window, comprising an elongated hollow sash balance casing having a wall structure with an elongated opening therein,

' a resilient sash balancing member anchored to said casing and disposed therein,

a lock carrier reciprocably mounted in said casing in guided relationship therewith and having a fulcrum thereon,

and an approximately T-shaped locking member having a fulcrum rest-tiltably engaging said fulcrum, a trigger arm extending from said fulcrum rest toward 9 10 said opening, and a preponderant locking arm of ability with said locking member at predetermined heavier weight than said trigger arm extending away pp i e i g Positio s of its mOfiOH.

from said fulcrum rest toward one of said walls and having a locking edge thereon normally urged by References Cited by the Examiner the preponderant Weight of said locking arm into 5 UNITED STATES PATENTS locking engagement with the wall structure at a loca 2 933 757 4 50 Almendinger, tion spaced y from i p g, 2,989,773 6/61 Perry 2o 52.2 X

said lock carrier being provided with a pair of spaced stop portions disposed in motion-limiting engage- HARRISON MOSELEY, Primary Examiner- 

1. A SELF-LOCKING AUTOMATICALLY-RELEASING SASH BALANCE FOR A REMOVABLE SASH WINDOW, COMPRISING AN ELONGATED HOLLOW SASH BALANCE CASING HAVING A WALL STRUCTURE WITH AN ELONGATED OPENING THEREIN, A RESILIENT SASH BALANCING MEMBER ANCHORED TO SAID CASING AND DISPOSED THEREIN, A LOCK CARRIER RECIPROCABLY MOUNTED IN SAID CASING IN GUIDED RELATIONSHIP THEREWITH AND HAVING A FULCRUM THEREON SPACED INWARDLY AWAY FROM SAID OPENING, AND AN APPROXIMATELY T-SHAPED LOCKING MEMBER DISPOSED SUBSTANTIALLY IN ITS ENTIRETY WITHIN SAID HOLLOW CASING AND HAVING A FULCRUM REST TILTABLY ENGAGING SAID FULCRUM, A TRIGGER ARM EXTENDING FROM SAID FUL- 